1. Field of the Invention
The present invention relates to a method of operating a firing installation. It also relates to a burner for carrying out the method as claimed in claim 1 and to a method of operating this burner.
2. Discussion of Background
In firing installations for, for example, central heating systems, the fuel in a conventional type of construction is injected via a nozzle into a combustion chamber and burned therein with introduction of combustion air. In principle, operation of such firing installations is possible with a gaseous or a liquid fuel. When a liquid fuel is used, good atomization of the fuel and good mixing with the combustion air must be achieved in order to obtain minimum emissions of NO.sub.x, CO and unburned hydrocarbons (UHC).
Accordingly, if a liquid fuel is used, the quality of the combustion with respect to low pollutant emissions largely depends on whether it is possible to provide an optimum degree of mixing of the fuel/fresh air mixture, i.e. to ensure possible complete gasification of the liquid fuel. Reference should also be made to the problems in the field of a part load operation, as discussed in EP-A2-0,166,329. Various other disclosed attempts of operating with a leaner mixture in part load operation have regularly failed since, in this case, the burn-up rate deteriorates and the CO/UHC emissions rise very steeply. In technical language, this state is circumscribed by the term CO/UHC/NO.sub.x pitch. The way of providing a premixing zone for the fuel/fresh air mixture upstream of the actual combustion zone also does not lead to the goal of a safe and reliable burner, since it involves the imminent risk of back-ignition from the combustion zone into the premixing zone causing damage to the burner.